Will it though?
If I join from Linux using Ferdium or any other browser what will prevent me from using any screenshooter? Or will web be considered an unsupported platform?
It's definitely not true that this feature breaks support for devices not owned by the manufacturer. The follow on question about whether all possible web clients / operating systems would be supported, I don't know. The article just says that web is supported.
“Web is supported” in this instance just means “the web, but only when mediated by google, microsoft or apple”, which is not the web as far as I'm concerned.